Numerical Simulation and Experimental Study of Heat-fluid-solid Coupling of Double Flapper-nozzle Servo Valve

The double flapper-nozzle servo valve is widely used to launch and guide the equipment. Due to the large instantaneous flow rate of servo valve working under specific operating conditions, the temperature of servo valve would reach 120℃ and the valve core and valve sleeve deform in a short amount of time. So the control precision of servo valve significantly decreases and the clamping stagnation phenomenon of valve core appears. In order to solve the problem of degraded control accuracy and clamping stagnation of servo valve under large temperature difference circumstance, the numerical simulation of heat-fluid-solid coupling by using finite element method is done. The simulation result shows that zero position leakage of servo valve is basically impacted by oil temperature and change of fit clearance. The clamping stagnation is caused by warpage-deformation and fit clearance reduction of the valve core and valve sleeve. The distribution roles of the temperature and thermal-deformation of shell, valve core and valve sleeve and the pressure, velocity and temperature field of flow channel are also analyzed. Zero position leakage and electromagnet＇s current when valve core moves in full-stroke are tested using Electro-hydraulic Servo-valve Characteristic Test-bed of an aerospace sciences and technology corporation. The experimental results show that the change law of experimental current at different oil temperatures is roughly identical to simulation current. The current curve of the electromagnet is smooth when oil temperature is below 80℃, but the amplitude of current significantly increases and the hairy appears when oil temperature is above 80℃. The current becomes smooth again after the warped valve core and valve sleeve are reground. It indicates that clamping stagnation is caused by warpage-deformation and fit clearance reduction of valve core and valve sleeve. This paper simulates and tests the heat-fluid-solid coupling of double flapper-nozzle servo valve, and the obtained results provide the reference value for the design of double flapper-nozzle force feedback servo valve.

Atrial electromechanical coupling parameters after transcatheter aortic valve replacement

The article entitled Effect of transcatheter aortic valve replacement on P-wave duration, P-wave dispersion and left atrial size by Dursun, et al. has contributed to our knowledge regarding the positive effects of transcatheter aortic valve replacement （TAVR） procedure on atrial electrical remodeling. In this study, TAVR procedure led to a decrease on P-wave duration and P-wave dinner,inn

eSie Valves四维自动定量分析评价主动脉瓣-二尖瓣机制的应用

目的探讨eSie Valves四维自动定量分析系统在主动脉瓣-二尖瓣偶联机制定量评估中的应用价值。方法2018年9～12月入选38例卵圆孔未闭或房颤患者,应用经食管三维超声心动图(3D-TEE)采集主动脉环及二尖瓣环三维图像,运用eSie Valves四维自动定量分析系统重建主动脉瓣-二尖瓣三维模型,自动获得主动脉瓣及二尖瓣相关参数,以及主动脉瓣环与二尖瓣环间夹角、主动脉瓣-二尖瓣中心距离,观察其在全心动周期变化规律,并取最大值及最小值进行比较。结果入选患者均获得满意图像及完整的心动周期动态分析结果,所有参数最大值及最小值的差异均有统计学意义(P <0. 001)。二尖瓣环与主动脉瓣环面积呈相反变化趋势,二尖瓣环面积于舒张早期达到峰值(866. 4±160. 4) mm^2,主动脉瓣环面积处于最小值(413. 5±62. 9) mm^2;收缩期二尖瓣环面积最小值(621. 7±149. 0) mm^2,主动脉瓣环面积达到峰值(517. 2±71. 8) mm^2。等容收缩期中心距离最大(21. 6±1. 4) mm,其后随左心室容量变化致等容舒张期达到最小值(18. 4±2. 0) mm;主动脉瓣-二尖瓣夹角在收缩末期最小(94. 3±12. 7)°,舒张期达到峰值(124. 8±9. 3)°。结论 eSie Valves四维自动定量分析系统能重建主动脉瓣根部、二尖瓣及二者空间偶联模型,为主动脉瓣-二尖瓣偶联机制定量研究提供了新的方法。

Fluid-solid coupling numerical simulation of charge process in variable-mass thermodynamic system

Abstract： A joint solution model of variabk：-mass flow in two-phase region and fluid-solid coupling heat transfer, concerned about the charge process of variable-mass thermodynamic system, is built up and calculated by the finite element method （FEM）. The results are basically consistent with relative experimental data. The calculated average heat transfer coefficient reaches 1.7~105 W/（m2. K）. When the equal percentage valve is used, the system needs the minimum requirements of valve control, but brings the highest construction cost. With the： decrease of initial steam pressure, the heat transfer intensity also weakens but the steam flow increases. With the initial water filling coefficient increasing or the temperature of steam supply decreasing, the amount of accumulative steam flow increases with the growth of steam pressure. When the pressure of steam supply drops, the steam flow gradient increases during the maximum opening period of control valve, and causes the maximum steam flow to increase.

Research on valve core’s clamping stagnation of double flapper-nozzle servo valve

Due to great changing of instantaneous temperature of hydraulic oil of double flapper-nozzle servo valve, thermal deformation between valve core and valve sleeve may result in catching phenomenon of valve core, and then the reliability of servo valve could be affected seriously. The work focuses on a particular model of double flapper-nozzle servo valve and establishes three dimension couple models of liquid-solid-thermal under extreme operating condition. The transmission route and dissipative mechanism of heat is revealed and thermal deformation behavior of valve core and valve sleeve is researched. A change law of the key fit clearance under the effect of thermal expansion and warp deformation is explored, the source of catching phenomenon of valve core is identified, and then preventive measure and improvement can be proposed. In order to verify the correctness of theoretical analysis, the moving smoothness of deformed valve core and reground valve core under the circumstance of high-temperature hydraulic oil on electrohydraulic servo valve static characteristics test table is compared and tested. The results show that as oil temperature rises, relative deformations between valve core and valve sleeve in different direction at a same cross-section are not equal, and then the key fit clearance is less than the initial value. Relative deformations in the same direction at different axial position are not equal, the deformations of middle and two ends are maximum and minimum values respectively, and then warp deformation of valve core occurs. When oil temperature is higher, the relative deformations between valve core and valve sleeve is larger, the moving smoothness of valve core gets worse, and the catching phenomenon of valve core occurs. Axial deformation of valve sleeve and valve core at different axial position is different, and the opening coefficient and stability of servo valve could be affected, especially the operation circumstance of small opening. The study can provide some guidance for designing double nozzle flapper servo valves.

A NEW APPROACH FOR PREDICTING DYNAMIC BEHAVIOR OF EXTRA-HIGH SPEED DIGITAL VALVE

High speed digital valves are devices ideally suited for the direct interface of fluid power components to digital computers due to their on/off characteristics. In this paper, a model of an extra high speed digital valve applied in fuel injection system was presented. In order to get the ability of fast response and a simple construction, a new concept for designing and predicting the valve was presented herewith. A new predicting simulation model of the entire test stand was utilized in order to parameterize the model against measured data. The new model predicts transient valve behavior and the proper dynamic coupling between the electrical, magnetic, mechanical and fluid subsystems. Based on the model and simulation, a prototype valve with working pressure of 120 MPa and frequency of 2 kHz was designed and fabricated, its experimental and prediction results for armature motion show excellent agreement.

Electrical controllable spin valves in a zigzag silicene nanoribbon ferromagnetic junction

We propose two possible spin valves based on a zigzag silicene nanoribbon（ZSR） ferromagnetic junction. By using the Landauer–B u¨tikker formula, we calculate the spin-resolved conductance spectrum of the system and find that the spin transport is crucially dependent on the band structure of the ZSR tuned by a perpendicular electric field. When the ZSR is in the topological insulator phase under a zero electric field, the low-energy spin transport and its ON and OFF states in the tunneling junction mainly rely on the valley valve effect and the edge state of the energy band, which can be electrically modulated by the Fermi level, the spin–orbit coupling, and the local magnetization. When a nonzero perpendicular electric field is applied, the ZSR is a band insulator with a finite energy gap, the spin switch phenomenon is still preserved in the device and it does not come from the valley valve effect, but from the energy gap opened by the perpendicular electric field. The proposed device might be designed as electrical tunable spin valves to manipulate the spin degree of freedom of electrons in silicene.

右心室-肺动脉耦连在心血管疾病中的应用进展

右心室-肺动脉耦连(RVPAC)是右心室收缩力与后负荷的关系。当右心室功能和肺血管阻力适配时可维持正常RVPAC,而右心室收缩力不足以匹配后负荷时则导致右心室功能障碍。RVPAC在许多心血管疾病病理生理及疾病进展中起重要作用,是患者预后的决定性因素,早期、准确评估RVPAC对于患者病情评估、临床治疗决策、危险分层及预后判断具有重要意义。目前RVPAC的测量方法较多,分为侵入性与非侵入性方法,其中非侵入性方法主要与超声相关。本文就RVPAC的病理机制、测量方法、不同方法优缺点及其在不同心血管疾病中的应用价值进行综述。

基于某锅炉用闸阀闸板面密封失效研究

某锅炉用楔形双闸板闸阀在实际使用过程中出现了闸板密封面磨损严重、阀体上导轨槽与闸板上导轨翻边现象,这会对阀门密封面及其整体结构造成很严重的破坏,影响使用寿命。结合尺寸链理论对导轨间隙尺寸进行分析,对导轨槽挤压应力进行校核,并基于热固耦合仿真分析方法对其进行模拟。结果表明:由于导轨间隙尺寸过大,闸板提起时不能及早使两密封体完全脱离产生磨损,导轨结构尺寸的不合理使其导轨上挤压应力不满足要求,在长期高压高温工况使用下,阀体导轨槽产生屈服被压溃,致使闸板倾斜挤压密封面,造成进一步的磨损破坏。根据研究结果对闸板上导轨结构尺寸进行优化改进,满足了所需应力要求,减小磨损程度。此研究可为该类阀门的设计及优化提供一定的参考依据。

Coupling behavior between adhesive and abrasive wear mechanism of aero-hydraulic spool valves

Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Secondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters during wear evolution process. Meanwhile, Archard model and three-body abrasive wear model were utilized for adhesive wear and abrasive wear, respectively. Furthermore, their coupling wear model was established by calculating the actual wear volume. Finally, from the result of formal test, all the required parameters for our model were obtained. The relative error between model prediction and data of pre-test was also presented to verify the accuracy of model, which demonstrated that our model was useful for providing accurate prediction of spool valve's wear life. (C) 2016 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.

Analysis of Thermal-Fluid-Structure Coupling and Resonance Forecast for Link Butterfly Valve Under Small Opening

When the link butterfly valve operates at a small opening degree in high temperature working conditions,it is prone to the problem that the valve is stuck,the strength is insufficient and the butterfly plate is violently vibrating.This paper shows simulation experiments of both thermal-fluid-structure coupling and resonance forecast about DN600 link butterfly valve in the working conditions of 250℃and 0.5 MPa by ANSYS software.The medium is mixed with compressed air and flue gas.Flow field characteristics of the valve and stress deformation,modal and flow-induced vibration of butterfly plate are analyzed when the valve opening is less than 30%.The results indicate that,when the valve opening is less than 30%,fluid flow is relatively smooth in front of butterfly plate,a large number of vortexes are found behind the butterfly plate,and fluid flow is greatly chaotic in this position.The equivalent maximum stress and deformation of butterfly plate are relatively large when the valve locates in openings between 10%and 30%;the intensity of the butterfly plate is enough;the axial deformation does not impact opening and closing of the valve.The butterfly plate is likely resonant when the valve opening is less than 10%.The research of this paper provides a crucial reference for flow field characteristics of link butterfly valve,an analysis of intensity and rigidity of butterfly plate,and a resonance forecast of butterfly plate when the valve works in small opening.

一种比例换向阀先导级用高速开关阀运动特性分析

为研究一种用于比例换向阀先导级的高速开关阀运动特性,通过编写UDF程序控制流体力、弹簧力和电磁力共同作用下的阀芯运动;通过动网格技术实现阀的流固耦合仿真,并获取阀芯精确的运动情况以及瞬态流场的变化。结果表明:编写的UDF程序能够精确地模拟实际工作时的阀芯运动状态,获得阀的开启时间为1.8 ms。该研究方法能够获得高速开关阀精确的运动特性,为高速开关阀产品的优化提供指导。

船用三通调节阀流-固耦合噪声数值模拟

针对船用PN10DN32三通调节阀噪声声压频谱、声指向性等声学特性规律不明确,噪声声压级是否满足使用要求的问题,基于流-固耦合理论,同时考虑流-固耦合面及流体域内的脉动声学激励源,开展阀门噪声数值模拟研究。分别对三通调节阀在80%及60%开度阀外1 m处的噪声进行数值模拟,分析研究噪声声压频谱特性及声指向性规律。结果表明:80%及60%开度下的噪声声压级分别为49.14 dB(A)、50.79 dB(A),均小于60 dB(A)的噪声限制,满足使用要求。该文为船用三通调节阀噪声数值模拟提供了理论及方法参考。

甘蔗收获机多路阀阀芯的温升及热变形仿真分析

多路阀是甘蔗收获机械液压系统的核心元件,用于控制多个工作装置的协同作业。针对其阀口压差变化大,节流温升明显,易造成阀芯变形卡滞的问题,对多路阀阀芯进行了流固热耦合仿真研究。利用Design Model软件抽取对应流道,并建立不同开度的多路阀流场仿真模型,导入ANSYS Workbench平台进行不同工况下的流固热耦合仿真,分析对比了双U形和三角形节流槽在不同开度、不同进出口压差工况下,多路阀内部流场的流体速度、阀芯温度及变形的情况。结果表明:双U形、三角形节流槽阀芯最高温度始终在节流槽处;随着阀进出口压差增加,油液的最大流速以及两种节流槽型阀芯的最高温度和最大形变量增大,但三角节流槽型阀芯变形相对较小;随着阀口开度的增加,三角节流槽型阀芯温度及最大形变量均小于双U形节流槽阀芯;三角节流槽型阀芯的最大形变量较双U节流槽型阀芯小25.1%。为农业机械多路阀阀芯节流槽设计提供了理论依据。

基于流固耦合方法的大口径闸阀减振分析

针对大口径楔式闸阀在启闭过程及小开度工况下易引起流激共振,产生较强的阀杆和闸板振动的问题,提出在阀后添加扩管的结构优化方法,以降低流体流态突变进而减小共振,并给出了3种具体的改进方式。通过对比分析改进前后闸阀管道液流系统的压力脉动、共振幅值,验证优化的可行性。研究结果表明:阀后添加扩管能够减小阀后涡旋和压力脉动,使阀内流体更快的趋于稳定;优化后阀门在1/16和1/8开度下的共振幅值由26.819 mm和2.347 mm减小为10.036 mm和1.959 8 mm,极大地降低了阀门在小开度下的共振幅值,有效减小了共振对阀门的损伤。压力脉动大幅值集中在小开度下低频区内(50 Hz),且脱落涡频率为26.72 Hz和28.44 Hz,当阀门系统处于二阶和四阶模态时,易产生涡激共振,应该避免在小开度工况及相应的频率范围内工作。研究结果可为大口径闸阀的减振优化提供参考。

大口径楔式闸阀振动诊断及减振优化

大口径楔式闸阀广泛应用于石油、化工管道系统,其常承受介质动压载荷与温度载荷的耦合作用;耦合载荷不仅会加剧阀门结构的变形,增加阀杆与阀盖的摩擦磨损,也会影响流体流态,严重时甚至会诱发流激振动,造成阀杆断裂。该文针对DN1200mm大口径闸阀实际工程应用中的阀杆断裂问题,采用过程离散分析法划分多阀板位置,利用ANSYS数值模拟技术可视化了闸阀流场的流动特征,基于傅里叶信号分析法揭示了流体域的压力脉动响应,并对阀门管道液流系统进行模态分析和谐响应分析,研究了特定行程下多物理场耦合作用的阀杆和闸板共振特性。结果表明:当闸阀启闭且行程较小时,阀后因闸板扰流作用出现大的卡门涡街和回流现象,流体压力脉动增大且流动紊乱,进而诱发阀门管道液流系统产生大的共振幅值,导致阀杆断裂。基于此,提出在阀后添加扩管,发现添加扩管可缓解阀后涡流和回流,减小压力脉动,进而避免流激共振的发生。该文还定性和定量分析了扩管尺寸对流体压力脉动和共振幅值的削弱作用,对比研究表明:扩管直径为1.3倍管径(1560mm)且长度为1倍管径(1200mm)时,减振效果最好。该文研究结果对大口径闸阀的减振优化研究具有一定的指导意义。

热电解耦提升机组灵活性研究

江苏徐矿综合利用发电有限公司实施供热改造,替代周边供热区域内3家热电厂以及69台小锅炉[1],承担起全区工业生产和居民采暖所需供热。随着华东地区新能源发电和区外来电份额逐年增加,电网对传统火电机组调峰能力和性能有了更高要求。供热系统出力与汽轮机负荷呈正比,冬季大流量供热期间,需要维持较高的电负荷,AGC调节能力不足,面临着流化床锅炉长期满负荷运行带来的返料器料腿烧红、加剧受热面磨损等问题,进行热电解耦提升机组灵活性势在必行。

双向复位高速开关电磁阀动态响应特性仿真研究

高速开关电磁阀作为典型的伺服液压系统执行元件,逐渐成为高精密液压系统的核心部件之一。针对双复位弹簧式高速开关电磁阀的动态响应特性开展研究,建立高速开关电磁阀的多场耦合动力学模型,系统研究了高速开关电磁阀阀芯内径、弹簧刚度、线圈线径、工作温度、控制频率及占空比等对高速开关电磁阀阀芯所受到的电磁力和阀芯运动位移的影响,得到了高速开关电磁阀的优化设计参数,为进一步研制响应速度快、性能稳定、流量及承压范围大、环境适应性强的高速开关电磁阀奠定了一定的理论基础。

特种车辆油气弹簧减振阀可靠性研究

油气弹簧减振阀为特种车辆悬挂装置中的重要部件,针对其应用中受高频载荷易损问题,提出基于Ansys Fluent的油气弹簧减振阀流固耦合可靠性研究方法。基于该方法建立减振阀中阀芯及阀座固体模型与周围油液流体模型,分析0.6、3.96、7.83 Hz激振频率下的减振阀工作状态,研究其安全系数及寿命。结果表明:减振阀阀座在颈部连接处、正对常通孔处易破坏;阀芯易损部位主要集中于阀杆处。研究结果可为减振阀可靠性分析提供参考,亦可服务于后续减振阀薄弱环节优化设计。

低速大扭矩水液压马达的深海性能迁移特性

为实现深海水液压机械手回转关节的稳定输出,研制了一种新型阀配流低速大扭矩水液压马达。搭建了其数学及物理模型,完成了马达与机械手腕部关节的集成设计,通过马达的AMESim仿真模型分析了深海环境对马达输出性能的影响。研究发现:随着海深的增加,马达的输出扭矩显著降低,输出转速也出现一定变化,环境压力从0 MPa增加至120 MPa的过程中,马达的输出扭矩累计降低了34%,最大稳定转速却较陆上工况增加了13%。此研究为马达的结构优化与深海作业控制提供了理论依据。